Stress transfer characteristics of sheathed strand in prestressed concrete beams: computational study

Strand debonding is a common approach used to control stress and reduce cracking at the ends of pretensioned concrete beams. However, damage in pre- tensioned beams with debonded strands during manu- facture has raised concerns about the use of debonding as currently specified. Numerical simulations were conducted in this study to improve understanding of the stress transfer characteristics of sheathed strand in pretensioned concrete elements. Nonlinear finite element models of small-scale prestressed concrete beam units in which concrete and strand were mod- eled with three-dimensional continuous elements were established with commercial software. The numeri- cal simulations were calibrated with experimental data, and results show that the lack of bond resistance along the debonded region maximizes the dilation of the strand after release. This effect may damage the concrete if there is tight contact between concrete and strand, which may result when using flexible, tight- fitting debonding material. This problem is eliminated if enough room is provided for strand dilation.